docs/sql-manual/sql-functions/scalar-functions/json-functions/json-array-ignore-null.md

---
{
    "title": "JSON_ARRAY_IGNORE_NULL",
    "language": "en",
    "description": "Generate a JSON array containing the specified elements. Returns an empty array when no parameters are passed."
}
---

# JSON_ARRAY_IGNORE_NULL
## Description
Generate a JSON array containing the specified elements. Returns an empty array when no parameters are passed.

## Syntax
```sql
JSON_ARRAY_IGNORE_NULL([<expression>, ...]) 
```

## Parameters
### Variable parameters:
- `<expression>`: Elements to be included in the JSON array. Can be single or multiple values of different types, including NULL.

## Return Value
[`JSON`](../../../basic-element/sql-data-types/semi-structured/JSON.md): Returns a JSON array composed of the parameter list.

## Usage Notes
- JSON_ARRAY_IGNORE_NULL implementation converts different types of parameters to JSON values by implicitly calling the [`TO_JSON`](./to-json.md) function, so parameters must be types supported by [`TO_JSON`](./to-json.md).
- NULL will be ignored. If you DO want to retain null values in the array, you can use the function [`JSON_ARRAY`](./json-array.md).
- If the parameter type is not supported by [`TO_JSON`](./to-json.md), you will get an error. You can first convert that parameter to String type, for example:
    ```sql
    select JSON_ARRAY_IGNORE_NULL(CAST(NOW() as String));
    ```
    > The NOW() function returns a DateTime type, which needs to be converted to String type using the CAST function
- If the parameter is a JSON string and you want to add it to the array as a JSON object, you should explicitly call the `JSON_PARSE` function to parse it as a JSON object:
  ```sql
  select JSON_ARRAY_IGNORE_NULL(JSON_PARSE('{"key": "value"}'));
  ```

## Examples
1. Regular parameters
    ```sql
    select json_array_ignore_null() as empty_array, json_array_ignore_null(1) v1, json_array_ignore_null(1, 'abc') v2;
    ```
    ```
    +-------------+------+-----------+
    | empty_array | v1   | v2        |
    +-------------+------+-----------+
    | []          | [1]  | [1,"abc"] |
    +-------------+------+-----------+
    ```
2. NULL parameters
    ```sql
    select json_array_ignore_null(null) v1, json_array_ignore_null(1, null, 'I am a string') v2;
    ```
    ```
    +------+---------------------+
    | v1   | v2                  |
    +------+---------------------+
    | []   | [1,"I am a string"] |
    +------+---------------------+
    ```
3. Unsupported parameter types
    ```sql
    select json_array_ignore_null('item1', map(123, 'abc'));
    ```
    ```
    ERROR 1105 (HY000): errCode = 2, detailMessage = Can not find the compatibility function signature: to_json(MAP<TINYINT,VARCHAR(3)>)
    ```
4. Map type parameters can be explicitly converted to JSON

    ```sql
    select json_array_ignore_null(1, cast(map('key', 'value') as json));
    ```
    ```
    +--------------------------------------------------------------+
    | json_array_ignore_null(1, cast(map('key', 'value') as json)) |
    +--------------------------------------------------------------+
    | [1,{"key":"value"}]                                          |
    +--------------------------------------------------------------+
    ```
5. JSON strings can be parsed with `json_parse`
    ```sql
    select json_array_ignore_null(json_parse('{"key1": "value", "key2": [1, "I am a string", 3]}'));
    ```
    ```
    +------------------------------------------------------------------------------------------+
    | json_array_ignore_null(json_parse('{"key1": "value", "key2": [1, "I am a string", 3]}')) |
    +------------------------------------------------------------------------------------------+
    | [{"key1":"value","key2":[1,"I am a string",3]}]                                          |
    +------------------------------------------------------------------------------------------+
    ```